Australian Targets

Friday, August 22, 2014

New research shows that the rate of ocean acidification in coral reef ecosystems is more than three times faster than in the open ocean, much more than previously thought. This has big implications for reef ecosystems around the globe suffering under multiple stressers of increased sea surface temperatures, nutrient and other pollution and commercial fishing pressures.

Biogeochemist researchers from Southern Cross University Led by recent graduate Dr Tyler Cyronak detailed this new insight in a study published in Geophysical Research Letters titled Enhanced coral reef acidification driven by regional biogeochemical feedbacks.

Ocean acidification is well documented in open waters. Cold waters like in the southern ocean can more readily absorb carbon dioxide, so ocean acidification was thought to be proceeding more rapidly in marine ecosystems in cooler waters (see my 2007 article: Scientists say Ocean Acidity Increasing at Faster Rate)

This new research highlights that coral reef waters are also rapidly acidifying. This research examined studies done in coral reefs since the 1960s and found that the rate of acidification in coral reef ecosystems was more than three times faster than in the open ocean.

To try and work out the cause of this more rapid ocean acidification the researchers developed a model based on work done at Heron Island in the Great Barrier Reef to discover that coral reef respiration may be the cause.

“Our model demonstrated that small changes in the biogeochemistry, or the way coral reefs breathe carbon dioxide, could be to blame,” said Dr Cyronak. “During the day coral reefs take up carbon dioxide because photosynthesis is dominant and at night they release carbon dioxide through respiration. Small changes to this natural daily cycle can have a big impact on the average acidity of coral reef waters.”

Professor Bradley Eyre, director of the Centre for Coastal Biogeochemistry Research and aslo a co-author of the study, outlined the global significance:

“The findings from this study are globally important because coral reefs are under a lot of pressure from climate change,” said Professor Eyre. “Ocean acidification in particular is expected to result in reef loss, which may now be worse than previously expected.”

Another study co-author Associate Professor Kai Schulz comented that increased inputs of organic material and nutrients could be responsible.

“More organic material can change the ratio of respiration to photosynthesis,” said Associate Professor Kai Schulz. “Coral reefs are generally balanced, but if respiration increases it can have a big effect on the average carbon dioxide levels of a reef.”

The good news is that if we can reduce the amount of agricultural runoff from agricultural production and nutrient pollution, this may slow the rate of acidification and the impact on coral reef ecosystems.

“I think there are some positives to these findings,” said Dr Cyronak. “Generally ocean acidification is thought of as a global problem. However, if the pH of a coral reef can be controlled by reducing runoff and terrestrial inputs there may be solutions to help offset the global problem of ocean acidification, or at least the increased threat, on a regional level.”

The abstract for the study reads in full:

Physical uptake of anthropogenic CO2 is the dominant driver of ocean acidification (OA) in the open ocean. Due to expected decreases in calcification and increased dissolution of CaCO3 framework, coral reefs are thought to be highly susceptible to OA. However, biogeochemical processes can influence the pCO2 and pH of coastal ecosystems on diel and seasonal time scales, potentially modifying the long-term effects of increasing atmospheric CO2. By compiling data from the literature and removing the effects of short-term variability, we show that the average pCO2 of coral reefs throughout the globe has increased ~3.5-fold faster than in the open ocean over the past 20 years. This rapid increase in pCO2 has the potential to enhance the acidification and predicted effects of OA on coral reef ecosystems. A simple model demonstrates that potential drivers of elevated pCO2 include additional anthropogenic disturbances beyond increasing global atmospheric CO2 such as enhanced nutrient and organic matter inputs.

In other research from 2012, Sea cucumbers have also been shown to increase the alkalinity of the reef water providing a buffer to the increasing acidity caused by ocean acidification.

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About Me

Time to leap out of the slowly boiling pot of earth's warming climate
into action on climate mitigation and adaption.
I don't want my children to ask why I didn't act after reading the
scientific reports of climate risks. I write on the
effects of human induced climate change, sea level rise, ocean
acidification, biodiversity loss, environmental and social impacts of
global warming, and climate protests from a Melbourne Citizen
Journalist.

A member of environmental NGOs and community groups for 30 years in Australia, currently living in Melbourne. I have been a Citizen journalist for the Indymedia network in Australia and worldwide from 2000, as an editor and contributor with Australia Indymedia and the global features collective. Since 2013 I have contributed many stories to Margot Kingston's citizen journalism website: nofibs.com.au. (See my article archive) I also post photoessays to Flickr and videos to Youtube and edit wikipedia as user Tirin. My website is takver.com where I can be contacted through the feedback form, the most reliable way to contact me. I can also be contacted through facebook and on twitter as @takvera.